Air-Smithing Guide (shimming, greasing, AoE, MOSFET's, etc.)

In this thread I will show you how to properly tune your AEG, build a MOSFET, and other tricks. If you are not comfortable doing any modifications to your AEG I would recommend having someone experienced do it for you. I myself along with all other members, moderators and administrators of ASCT will NOT be held responsible if you screw up or otherwise fail at upgrading or modifying your AEG or any other type airsoft gun.

AOE

AoE Stands for Angle of Engagement, which refers to the angle that the sector gear engages the pickup tooth (the very first tooth) on the piston.

On stock guns, it is usually very poor, and looks like this.

As you can see, the sector gear engages the pickup tooth at an upward angle which puts an unnecessary amount of force on the piston which will increase wear and tear.

To solve that issue, we need to adjust the angle to which it is engaged by the sector gear. To do that, we need to space back the piston so that the sector gear engages it at a more appropriate angle.

How do you space back a piston? There are two ways.

The first way is to place washers in-between the piston body and piston head as shown below.

The last, and my favorite way, is to install extra padding (preferably sorbo pad) on the cylinder head as shown below. I like this way the most as it is a 2-for-1 deal (sometimes 3). Not only does extra padding correct AoE, it also reduces stress on the front of the gearbox shell (and in some cases reduce the muzzle report).

The next step, is to shave teeth on the piston. You need to shave down the second tooth, and partially shave down the third tooth. Only shave down as much of the third tooth as necessary, do not shave more then 1/3 of the tooth, if more then 1/3 of the tooth is removed you compromise structural integrity. There must always be 2/3 remaining. It also helps to cut the third tooth at a slight angle.

On top is a properly modified piston, with the second tooth removed and the third tooth shaved down to about 2/3 of it's original length. On the bottom, is a piston with both the second and third tooth completely removed. You do NOT want to completely remove both teeth, that will compromise the structural integrity as there would be no third tooth for the gear to transfer to, which would mean the pickup tooth is engaged for to long which would increase wear and tear.

Shaving down the teeth is required for proper AoE. If you do not shave down the teeth, the sector gear will not be able to pass through and it will get caught on the wrong tooth as shown below. This will, quite obviously, damage the piston.

Once the teeth have been properly shaved, use enough washers and/or sorbo pad to space back the piston so the sector gear engages it at a flat angle, like this.

As you can see, the teeth now engage at a flat angle, like this // . Since the teeth engage each other at a flat angle, the energy is spread out on a larger surface area, thus increasing the life span of your piston. This modification has been around for many years, and it is a tried and true way to greatly increase the lifespan and durability of your piston. Do this properly and your piston will last a long time.

Shimming

Shims are little spacers that are placed on the gear axles. These are used to space the gears in a way so they line up correctly and do not grind against other gears or other internal components.

*Note* Other guides tell you to start with the spur gear. Those guides are incorrect and should be ignored. There no such mechanical application in which you start in the middle. This is how you are suppose to shim gears in all other mechanical applications, airsoft is no different.

First, take the pistol grip with the motor and the end cap, then screw it onto the top half of your gearbox shell with only the bevel gear installed. If you have a v3, v6 etc. just screw on the motor and motor cage.

Adjust the motor hight so the pinion gear makes full contact with the bevel gear just like this (obviously it would be inside the gearbox, but this is just so you get a good view of the what it should look like).

Then, place enough shims of the top face of the bevel gear so that it has enough clearance to avoid grinding against the gearbox shell and meshes well with the pinion gear. The bevel and pinion should be making as much contact as possible without hindering the movement or causing to much pressure.

Now that the bevel gear and pinion gear are aligned and meshing properly, you can remove the motor and pistol grip or motor cage.

Now place enough shims on the bottom of the bevel gear so it prevents the bevel gear from riding to low.

Screw the gearbox shell together and test the movement of the bevel gear. If shims need to be removed or added, do so to the bottom of the bevel gear, not the top face. If you alter the shims on the top face it will effect the way the pinion gear meshes with the bevel gear.

Next you install the spur gear. Put enough shims on the bottom of the spur so it has just enough clearance so it doesn't grind against the face of the gearbox shell, the anti reversal latch notches on the bevel gear, and also the bevel gear's bushing or bearing.

Then put enough shims on the top of the spur gear to prevent it from riding up. Screw the gearbox shell together and test the movement. Add or remove shims from the top of the spur gear if need be.

Then install the sector gear with enough shims on the bottom so it has enough clearance from the spur gear and cutoff leaver, and also makes as much contact as possible with the teeth on the piston.

This is wrong. The teeth are not fully contacting each other.

This is correct. The teeth are fully contacting each other.

Then put shims on the top of the sector gear to prevent it from riding up. Screw the gearbox shell together and test the movement. Add or remove shims from the top of the sector gear if need be.

All the gears should have as little play as possible, yet spin freely and without hesitation. I take my time shimming, and I shim gears to the point where they don't move side to side at all, so you may mistake them for being to tight considering you cannot feel them move from side to side, however they spin incredibly well when you move them and you can't even hear them spinning. That's the kind of precision and high tolorances you want, so take your time a get it right.

Greasing the gears (greasing the compression components is different, so please scroll down for that)

For gear grease, you need to use white lithium grease, which you can buy at hardware stores.

You don't need to put grease on the back of gears (the flat faces). The flat surfaces don't make contact with anything, so greasing them is pointless and will only make a mess. Yu want grease on areas that make contact with other components, like the gear teeth, piston rails, etc.

To apply grease, I would recommend to apply small drops to a cotton swap...or you can use your own hands if you don't mind getting dirty.

First, apply a small amount of grease to the face of the bushings and/or bearings.

Next apply some grease to teeth of the spur gear.

Then apply grease to the spur gears top axle

Flip it over and grease the bottom axle.

Then apply grease to the teeth that bevel out on the bevel gear.

Then apply grease to the next section of teeth as well as the axle.

Flip it over and grease the other axle.

Next, you grease the teeth on the sector gear and the axles.

Flip it over and grease the other axle.

Now put some grease on the rack gear (some call it piston teeth, but technically speaking it is considered a gear, more specifically a rack gear). Don't overdo it, you don't want excess grease falling off into the cylinder.

The final step is applying grease to the piston rails. Again, don't overdo it for the same reasons as above (you really don't want to overdo it anywhere for that matter).

And here is your finished work.

Maximizing Air-Seal

Maximizing your air-seal is important for your AEG's performance, consistency and efficiency. You will need some silicone gel, silicone oil and teflon tape (aka PTFE tape)

First, take the cylinder head and wrap teflon tape (aka PTFE tape) around the cylinder head. This will make it a tighter fit which will help the seal.

Then, apply a small amount of silicone oil or silicone gel to the piston head o-ring, and wrap it around an old cylinder. Heat it up with a heat gun or lighter. Don't burn it (the silicone oil or gel will help prevent burns). This will expand the o-ring which will increase the air seal. Another thing to do would be to buy a #14 o-ring from a hardware store.

Then apply a small amount of silicone gel to the piston head o-ring and spread it around evenly (silicon oil won't work well for the piston head o-ring and cylinder). The grease on the piston head will spread around the cylinder, so you don't really need to put any in the cylinder.

Next, remove the tappet plate and shave down the front face around the area of the air nozzle.

Before.

After

Now that the tappet plate is thinner, the air nozzle will move forward a bit further as shown below. This allows it to press harder against the lips of your hopup bucking, thus increasing the seal. This area of the tappet plate is exposed to ZERO stress, so don't worry about a thin tappet plate face breaking off, because it won't (unless you break it on purpose). You also don't have to worry about feeding, this won't effect feeding in any way, so you don't need to worry about that either.

Before

After

Inner Barrel Stabilization

Stabilizing your inner barrel is important to increase accuracy and consistency. When you fire an AEG, the energy that the piston makes when it slams into the front of your gearbox has to go somewhere, and what's in front of the gearbox?...the barrel. This energy will cause the barrel to vibrate, which will throw off your accuracy. Stabilizing your barrel will help prevent this. All you need is some teflon tape, and possibly silicon oil.

This mod is very simple, all you need to do is wrap teflon tape around the inner barrel, which will make it a tighter fit. Since it is a tighter fit, it will not vibrate as much as it did before, thus increase accuracy and consistency. Since it is a tighter fit, it may tricky to re-insert the barrel, so silicone oil can help. Just apply a small amount to the OUTSIDE of the inner barrel (NOT the inside, you don't want it there AT ALL), that will help it slide into place.

MOSFET's: what they are and how to make your own

What is a MOSFET? MOSFET stands for Metal Oxide Semi-conductor Field Effect Transistor. These devices completely remove the load from your conventional open trigger switch, thus preventing it from burning up when using a powerful battery such as the common 11.1v LiPo. MOSFET's are vital upgrades if you plan on using a powerful battery. When using powerful batteries, your trigger contacts will arc and burn up. A MOSFET will prevent this and fix the problem 100%. Without going to deep into how these work and boring you to death as I probably already have (but hey, at least you may have learned a thing or two in the process) I'll just show you what you need to make your own. With all the different MOSFET units on the market ranging from $25, $40, heck even $100+, you may think this is going to be expensive...wrong... Fact of the matter is, MOSFET's are dirt cheap, they just happen to have a very high resell value which is why you see these go for more then twice what they are worth. You can build a basic MOSFET using only $5 worth of basic electronic devices.

What you need;

-Various sizes of shrink tube

-Some good wire for the main wire assembly (I prefer silver coated multi-strand wire with either PVC or silicone insulation. For size, I use 14awg or 12awg when I can, but in some guns with tight spaces, you may need to bump it down to 16awg or 18awg. Don't use anything thinner then 16awg in an upgraded or high performance gun)

-Some extra-thin wire for the gate (size doesn't matter, so to save space use something thin such as 22-24awg)

-30k ohm resistor

-100 ohm resistor

-IRL3034 MOSFET chip

-Soldering equipment

Pic of everything.

Caution: Do NOT over heat the MOSFET chip, so try not to hold the soldering iron to the MOSFET for more then a second or two, let it sit and cool down if necessary. Do NOT cross-wire the leads (with the exception of soldering the resistor to the two outside leads).

Other things you should know: The MOSFET chip has three "leads" or "prongs". The first one on the left is called the gate lead, the middle is called the drain lead (goes to the motor) and the final lead on the right is your source lead (goes to the battery). There are different MOSFET types and styles, I like to use the basic 3034 MOSFET as it has enough load tolerances to meet our high standards. Years ago, people used weaker MOSFET's such as the 1404, but remember we did not have as high standards then, lipo's were not popular, 400fps was about the max anyone dared to push, etc. Now a days, people have guns shooting 600+fps reliably and people have started using powerful batteries such as 11.1v, heck even 14.8v LiPos, so the 3034 is what you should be using.

The first step is to cut a piece of shrink tube and insulate your 30k ohm resistor as shown.

Then you want to bend the rods so it fits the two outside leads on your MOSFET chip.

Then solder them in place.

Now take your 100 ohm resistor and solder it to the lead on the left side. This is your "gate" lead. Note: you may need to trim the rods on your 100 ohm resistor so it isn't to long.

Now solder on your thin piece of wire to the end of the 100 ohm resistor. This is your "gate" wire.

Once again, insulate your work with some shrink tube.

Now solder on a piece of your larger main wire to the right side lead, or the "source" lead. This is now your "source" wire.

Insulate it with shrink tube, then bend it back so it faces upwards. Be carful not to be to rough or you'll snap the lead.

Now solder on another piece of wire to the middle, or "drain" lead. This is now your "drain" wire.

And again, insulate your work with shrink tube.

Now all you have to do is insulate the entire unit with one large piece of shrink tube.

You are finished! Here is a picture of your finished work. For size comparison, a deans connector has been placed on the side. As you can see these are very small and take up hardly any space.

Here is a diagram on how you wire the MOSFET into your gun (follow the SW-S diagram), thanks to extreme-fire. I'll create a more in depth guide on how it should be wired when I get the chance, probably in a few days.

Last edited by Age on Sun Jan 27, 2013 9:36 pm, edited 13 times in total.

Thanks a lot Age! This was more helpful than most of the other guides online. A quick question though, i'm not sure what Sorbo Pad's are, but i have something that looks similar to it. Its called a furniture mover, its like a hard padding that's black.

Sorbo (short for sorbothane) is generally somewhat soft. If this furniture moving stuff you have is a solid, it won't work. A piston slamming into a solid object is not what you want. I sell sorbo pads if you want them.

Sorbo (short for sorbothane) is generally somewhat soft. If this furniture moving stuff you have is a solid, it won't work. A piston slamming into a solid object is not what you want. I sell sorbo pads if you want them.

For the inner barrel stabilization, when you say that you don't want silicone in the inner barrel, do you mean its bad? Because I've always cleaned my inner barrel with a paper towel and silicone spray :]. Also, thanks for the whole page! Helps me, and most likely a lot of other people.

Silicon oil attracts dirt and grime, so in a way, its bad AND good. You want the oil on the paper towel so it pulls out as much dirt and grime as possible, but once you are done cleaning the barrel, you need to dry it out. So unless you want to completely disassemble the barrel and houp unit to dry it all out, don't get silicone oil inside of it.

Very good stuff. Idea... how about we delete comments, and sticky each one of these mods individually. That way they could be found easier. Also, we could just add a questions thread for each oneShimmingQuestions on shimmingAoEQuestions on AoEetc

That way it's easier to locate, the thread doesn't get clogged with random comments, and being stickied it'll stay near the top.

Also, disclaimer needs to be added:

Opening your gearbox voids any and all warranties. Doing modifications/repairs is at your own risk. Airsoftct.com nor forum members hold any responsibility for you using this tips/techniques to alter your replica. These guides are only to be used as a guide and if you are not comfortable performing such tips/techniques, please take your replica to a qualified professional.

for cleaining the inner barrel what else can you use besides silicon? would CLP work as it builds up a teflon coat over time which would be ideal for something along these lines. CLP is a gun cleaning oil if you didn't know. Thanks in advance.

Yes I can build an AB MOSFET, pretty much all you need to do is wire in a "P-Channel" MOSFET parrelel with the other (and make a few other adjustments). While I do know how to make them, it is NOT something I recommend. The only thing AB MOSFET's are good for is killing your motor faster, there is no gain.

really? I would have thought it would be somewhat beneficial to the spring because it wouldnt stay compressed between shots. my AEG is blowback anyhow so I can fire a few times until I see the piston fully forward. I just thought the AB MOSFET would be better. How does it cause the motor to wear quicker?Glad I asked.

Do you suggest this basic MOSFET as the best option then?I will def not be fronting the money for one of these burst fire computer ones...I just want to run my AEG a little more efficiently.

Yeah, a lot of people seem to think Active Braking is so important, but they have no idea. You really don't need to worry about decompressing the spring until you are completely finished using the AEG, in which case that can easily be done using a weak battery that won't over spin the gearbox. There is no need to have AB reset each and every shot you fire, it makes no sense. What AB does, is it applies a reverse current to the motor making it spin in the opposite direction to stop it instantly. This constant stop and go on the motor will damage the commutator and brushes due to excessive arcing which will also over heat the armature. Motors are simply not designed to work that way. AB is a cheap shortcut for people who are either to lazy or simply don't have the skill to fine tune their system so it works properly.

i just really dislike the sound of the start and end of the shooting cycle, the small wind up and wind down bothers me. so i use a powerful battery at only 400 FPS and an AB mosfet to stop that noise. GIM GBBRs are too damned unreliable and i wont see a P* box for my AK for a while yet.but still, i may get a DG drop in kit for it.

i wonder the same thing. i usually install a weaker motor, recommend using a weaker battery or put in a heavier spring. but if there is a way to stop that without changing those 3 things, id like to know.

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